<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Title</title>
    <style>
      .box {
        position: relative;
        margin: 0 auto;
        width: 600px;
        height: 300px;
        background-color: pink;
      }
      .block {
        position: absolute;
        width: 600px;
        height: 300px;
        background-color: rgba(0, 0, 0, 0.3);
        visibility: hidden;
      }
      .play {
        position: absolute;
        top: 50%;
        left: 50%;
        margin-top: -15px;
        margin-left: -15px;
        width: 30px;
        height: 30px;
        background-color: #ff8500;
        border-radius: 50%;
        line-height: 30px;
        text-align: center;
        color: white;
      }
    </style>
  </head>
  <body>
    <div class="box">
      <div class="block">
        <div class="play">></div>
      </div>

      <script>
        var box = document.querySelector(".box");
        var block = document.querySelector(".block");
        box.onmouseover = function () {
          block.style.visibility = "visible";
        };
        box.onmouseout = function () {
          block.style.visibility = "hidden";
        };
        block.onmouseover = function () {
          console.log(1);
        };
      </script>
    </div>
  </body>
</html>
